It is easy to calculate normal monthly expenses by tracking your expenditures over the course of 30 days. The problem is that many people then use these numbers for planning purposes, and are then surprised when things like car insurance or property tax bills pop up unexpectedly. A better way to deal with these "hidden expenses" is to calculate them ahead of time and handle them on a monthly basis just like any other bill. Each month simply set a fixed amount of money aside in a separate account to pay for hidden expenses when they pop up.
The calculator below will help you to discover all of your hidden expenses. Its goal is to try to remind you of all of the different bills or expenses that crop up just once or twice a year. The calculator will determine a total amount due for all of these hidden bills and then divide that amount by twelve to give you an accurate monthly set-aside number.